California's massive high-speed rail project could save up to $2 billion -- and hundreds of homes -- by expanding and sharing existing tracks through the L.A.-O.C. region, local transit leaders argue.

Some critics worry that the L.A.-Anaheim segment will duplicate existing Metrolink and Amtrak service, both of which have the potential to go 110 mph if improvements are made.

It "isn't practical," to start with that segment said Michael McGinley, who previously headed Metrolink's engineering department and has worked on the local high-speed rail project as a consultant. "The first $4 billion should not be spent on that little spur. It overlaps and competes with an existing service."

Richard Katz, an influential Los Angeles transportation official who recently joined the high-speed rail board, is among those pressing less costly design models. "You've got to be realistic and take a hard look at what the demand is" between Los Angeles and Anaheim, said Katz, a former state Assembly leader who also sits on the MTA and Metrolink boards.

Up to $2 billion might be trimmed from the local segment's costs by improving and sharing existing track wherever possible, Katz and Kempton said.

Leahy, who sees great potential benefit in the bullet train project, said he is confident that high-speed rail and other services could operate safely on shared track.

The current bullet train plans would cause severe problems for seven cities, said Richard R. Powers of the Gateway Cities Council of Governments, a coalition of Los Angeles-area municipalities. He complained that the group's concerns have been largely ignored since 2004. A formal cooperation agreement was reached only recently, he said. "Now we have a constructive dialogue that we should have had years ago."